1. Field of the Invention
The present invention relates to a sulfonated poly(arylene ether) copolymer and a polymer electrolyte film using the same, and more particularly, to a sulfonated poly(arylene ether) copolymer that has a crosslinking structure in a polymer chain, and in and at an end of a polymer chain, and a polymer electrolyte film that is crosslinked by using the same.
2. Description of the Related Art
The fuel cell is the electrical energy transforming system that converts the chemical energy into the electrical energy with the electro chemistry reaction that invented by Grove in the 19th century. The fuel cell was used as the special purpose for 1960's like the Gemini spaceship, but it is expected to be used as the engine power of the non-polluted vehicle from the end of 1980's, and research and development about this all over the world actively proceed as the alternative energy corresponding to the increment of explosive population and electricity consumption.
In particular, since total pollutant load control of the carbon dioxide through the Green Round (convention on climatic change) and the low-pollutant vehicle obligatory sale have been being near at hand, the motor company of every country hurries the development of the pollution-free car like the fuel cell vehicle. In addition, the fuel cell can be immediately used for the munitions purpose power generation including the field stand small scale power generation of building and partial area, submarine, mobile communications and the like. This fuel cell does not have the function of accumulating the electricity, but is a clean high efficiency generation apparatus in which efficiency is high as the generation device in comparison with the preexistence internal combustion engine, the fuel-use quantity is less, and the environment load substance that includes sulfur oxides (Sox), nitric oxide (NOx) and the like are almost not discharged, and is expected as the solution plan of the environment problem in respects to the fossil fuel usage.
The polymer electrolyte that is used as a cation exchange resin or a cation exchange film in the fuel cell has been used for decades and continuously studied. Recently, as the medium that transfers the cations that are used in the direct methanol fuel cell (DMFC) or the polymer electrolyte membrane fuel cell (PEMFC), many studies in respects to the cation exchange film have been made.
Currently, as the cation exchange film that is extensively commercialized in the fuel cell field, there is a Nafion™ film that is a polymer including the hyperfluoride sulfon acid group. When the film includes moisture in the saturated moisture content, it has the ion conductivity of 0.1 S/cm and the excellent mechanical strength and chemical resistance, and also has the stable performance as the electrolyte film so that it is used in the fuel cell for vehicles. In addition, as the commercial film that has the similar shape, there are an Aciplex-S film that is manufactured by Asahi Chemicals, Co., Ltd, a Dow film that is manufactured by Dow Chemicals, Co., Ltd., a Flemion film that is manufactured by Asahi Glass, Co., Ltd., a GoreSelcet film that is manufactured by Gore & Associate, Co., Ltd. and the like, and an alpha or beta type perfluorinated polymer has been developed in Ballard Power System, Co., Ltd.
However, since the above films are costly, there is a difficulty in mass production because of the critical synthesis methods, there is a methanol crossover phenomenon in an electric energy system such as a direct methanol fuel cell, and they have the low proton conductivity at the high temperature or the low temperature, thus showing the property in which the efficiency is largely reduced as the cation exchange film, they are used for the limited purpose.
Because of these disadvantages, many studies have been made in respects to the cation exchange film in which a non fluorine system is substituted and fluorine is partially substituted, and a representative example thereof includes a sulfonated poly(phenylene oxide) system, a poly(phenylene sulfide) system, a polysulfone system, a poly(para-phenylene) system, a polystyrene system, a polyether ether ketone system, a polyimide and the like.
However, since their ion conductivities are in proportion to the degree of sulfonification, in the case of when they are sulfonificated over the critical concentration, the reduction of molecular weight cannot be avoided, there is a disadvantage in that it cannot be used over a long period of time because of the reduction of the mechanical properties in the hydration, thus in order to improve this, a method for producing the polymer using the sulfonated monomer and a method for selectively sulfonating the polymer have been studied and developed [U.S. Pat. Nos. 5,468,574, 5,679,482, and 6,110,616], but the high temperature stability and the problems that occur in use over a long period of time are not completely avoided.
Therefore, there is a need to develop a novel material that has the excellent electrochemical property, and high temperature stability, and can be easily produced for a thin film.